A recently derived representation of the Gibbs free energy of a defect process in terms of the thermoelastic properties of the host crystal is shown to be applicable to the calculation of the activation volume for the diffusion of impurities in solids. The experimental data for the diffusion of several metals (Ag, Au, Cu, Hg, Zn, Sn, Tl, Ni, Pd) in lead and the self‐diffusion are discussed showing a fair agreement with the theoretically determined activation volumina.